The present invention relates to energy cells and particularly to energy cells having an improved cathode material.
The prior art includes U.S. Pat. No. 3,484,295 to Dawson, issued Dec. 16, 1969, which discloses a battery having a cathode comprising principal active materials such as divalent silver oxide or sulfur and a secondary masking layer of a material such as monovalent silver oxide. The patent, however, does not disclose the use of a mixture of divalent silver oxide and sulfur to provide a lower voltage, higher capacity energy cell for watch use. U.S. Pat. No. 3,121,028 to Story, which issued Feb. 11, 1964, discloses the use of various sulfur compounds as depolarizers but does not disclose the use of a sulfur and silver oxide mixture as a cathode material.
U.S. Pat. No. 3,615,858 to Luis Soto-Krebs, which issued Oct. 26, 1971, describes a means for achieving a single potential discharge from a multivalent oxide, such as divalent silver oxide by providing a second layer of monovalent silver oxide as an intermediate conductor to give a lower voltage This patent recognizes the problems inherent in using divalent silver oxide as a cathode material. Interestingly, recent U.S. Pat. No. 3,853,623 issued Dec. 10, 1974 to Stuart M. Davis also proposes the use of divalent silver oxide but with a gold additive as a cathode material. The gold additive is intended to improve the stability of the divalent silver oxide. While recognizing the advantageous properties of divalent silver oxide as a cathode material, both Soto-Krebs and Davis are attempting to deal with the compensating negative factors but in a different way than applicant proposes.
Other prior art patents of interest include U.S. Pat. No. 3,057,944 to Ruetschi which issued on Oct. 9, 1962, U.S. Pat. No. 3,716,403 to Braun which issued Feb. 13, 1973, and U.S. Pat. No. 3,716,409 to Cairns which issued Feb. 13, 1973. These patents are not intended to be an all-inclusive listing of pertinent prior art patents but they tend to be representative of the art of interest.
One of the disadvantages of the prior art wherein divalent silver oxide is employed as a cathode material in energy cells is that it produces a higher initial voltage which is unsuitable for use in electrical or electronic watches. The divalent silver oxide also discharges at two distinct potentials as the material is first reduced to monovalent silver oxide and then to metallic silver. The emphasis in the new generation of watches particularly of the quartz crystal variety is on accuracy, and variations in the battery voltage adversely affect the accuracy of thes watches. Consequently, the present invention which provides the higher capacity of divalent silver oxide while supplying the lower voltage of the more stable monovalent silver oxide is a considerable improvement in energy cell design. Another important consideration in electric and electronic watches design is battery life and this requirement is readily met by the energy cell of the present invention.